Key Engineering Materials Vol. 625

Abstract: This paper presents the design, fabrication and control of a piezoelectric-type droplet generator which is applicable for on-line dispensing. The piezoelectric-actuated dispensing system consists of a linear piezoelectric motor (LPM) actuated table, a plastic syringe, a nozzle, a linear encoder and a PC-based control unit. Adaptive wavelet neural network (AWNN) control is applied to overcome nonlinear hysteresis inherited in the LPM. The adaptive learning rates are derived based on the Lyapunov stability theorem so that convergence of the tracking error can be assured. Unlike open-loop dispensing system, the system proposed can potentially generate droplets with high accuracy. Experimental verifications including regulating and tracking control are performed firstly to assure the reliability of the proposed control schemes. Real dispensing is then conducted to validate the feasibility of the piezoelectric-actuated drop-on-demand droplet generator. The results demonstrate that the proposed scheme works well in developing the piezoelectric-actuated drop-on-demand dispensing system.

Abstract: In this paper, based on the study of microbiological hazards real-time automatic alarm system for space applications and the “function integrated and structure miniature” of the microfluidic real-time PCR detection system, we have developed an integrated control system based on the MCU micro-processing chip for the control of constant temperature and sampling flow velocity of microfluidic PCR system. We have used the flexible polyimide film instead of traditional elements such as copper to facilitate the flow structure, which is characterized by small size, light weight and excellent heat transfer efficiency, applicable to the space environment. For the PID parameter tuning, by simulating the Z-N method of engineering turning based on the MATLAB/Simulink, a simple and efficient method for PID parameters turning is proposed in this paper. The practical application shows that the system is simple, strong applicability, high control accuracy, process visualization, fully automation control and adapt to the requirements of the space environment. It satisfies the development requirement of making the structural miniature and the function integrated. It can achieve the requirements of space applications by correcting and calculating the detection system in the conditions of weightlessness.

Abstract: Over the past few decades, vision based alignment has been accepted as an important technique to achieve higher economic benefits for precision manufacturing and measurement applications. Also referred to as visual servoing, this technique basically applies the vision feedback information and drives the moving parts to the desired target location using some appropriate control laws. Although recently rapid development of advanced image processing algorithms and hardware have made this alignment process an easier task, some fundamental issues including inevitable system constraints and singularities, still remain as a challenging research topic for further investigation. This paper aims to develop a visual servoing method for automatic alignment system using model predictive control (MPC). The reason for using this optimal control for visual servoing design is because of its capability of handling constraints such as motor and image constraints in precision alignment systems. In particular, a microassembly system for peg and hole alignment application is adopted to illustrate the design process. The goal is to perform visual tracking of two image feature points based on a XYθ motor-stage system. From the viewpoint of MPC, this is an optimization problem that minimizes feature errors under given constraints. Therefore, a dynamic model consisting of camera parameters and motion stage dynamics is first derived to build the prediction model and set up the cost function. At each sample step the control command is obtained by solving a quadratic programming optimization problem. Finally, simulation results with comparison to a conventional image based visual servoing method demonstrate the effectiveness and potential use of this method.

Abstract: There have been some devices for rehabilitations of upper limb such as electronic device and mechanical device which is well-known as the passive one. These devices make the motion of upper limbs and stimulate the wrist, elbow, shoulder joints with muscles. This motion does by using the patient’s normal hand (left or right hand) and rotating the wounded hand’s wrist to be recovered by the clockwise or counterclockwise with some angles. Electronic devices for upper limb rehabilitation have the advantage that the electronic ones can supply various rehabilitation exercises to the patients. However these electronic devices include relatively expensive components such as various kinds of sensors, controllers, and display device. Therefore, the prices of implementation are too expensive. On the other hand, in conventional passive upper limb rehabilitation, the patients grasp the both handles without any mechanical links. It does not supply proper rehabilitation motion because the normal hand does not supply the rehabilitation motion to hand to be recovered. So to speak, this is not proper to patients with the one hands trouble such as hemiplegic patients, by himself without the aids of any other persons. In this paper, we describe the mechanical device for rehabilitations of wrist and the proposed handles to be attached in this mechanical device. This proposed handles can generate the three angle motion of wrist such as the roll, pitch and yaw. This proposed device has some features that this device can be implemented with lower costs than electronic devices and can be used whatever the wounded hand is right or left by selecting the lever. Further, when the patient has the rehabilitation exercise intent, the patients can easily use the proposed upper limb rehabilitation devices without the aid of the rehabilitation therapist the energy source is the normal hands of the patients.

Abstract: In the design of upper limb rehabilitation robots, critical issues to be considered are large workspace with minimum singularities to cover enough patients’ upper limb range of motion and higher manipulability for the patients to easily and freely move their arm with applying almost the same force to every direction in a given posture. This paper presents an analysis of the suggested kinematic design considerations of five-bar planar mechanism according to the actuator locations. A comparison between two different five-bar linkage types is given. Finally, several open challenges for the applicability of five-bar planar mechanisms are discussed from the kinematic point of view to upper limb rehabilitation robots.

Abstract: As it is well-known, the stroke is known to be a cerebrovascular disease due to circulation disorders. Physical disabilities do remain due to nerve damages after strokes occur. These physical disabilities of the patient can be reduced by the rehabilitation treatment. This effect of rehabilitation appears with improvements of motor function. In order to evaluate the improvements of this motor function, therapists have used Fugl-Meyer assessment method (FMA). FMA method consists of fifty command motions such as thirty three command motions for motor function’s assessment of upper limbs and seventeen command motions for lower limbs. Further FMA method suggests three scores per each command motions. So to speak, in the FMA method, if the patients perform perfectly a given command motion, then they receive 2 points in a given command motion. Also if the patients cannot perform, they receive 0 point. Finally, if the patients perform partially, they receive 1 point. FMA method has a limit that cannot suggest exact assessments of the recovering patients. For the example, improvements of motor function of a patient cannot be evaluated from the initial stroke to full recovery. So it is hard to accurate diagnosis about patient's improvement. On the other hands, rapid upper limb assessment (RULA) method is suggested to evaluate the fatigue of muscle in a working environment. This RULA method suggests more detailed and quantitative assessment with diagnostic approaches than FMA method.

Abstract: In this study, aluminum alloys were subjected to nitriding at 823 K for 0–18.0 ks using alumina and magnesium powders for improving their radiation performance. After nitriding, aluminum nitride films were formed on the aluminum substrate. The thickness of the formed films varied from 1.5 to 11 μm, and the color of the film surface was dark brown or black. The thickness of the aluminum nitride film increased with an increase in the treatment time. X-ray diffraction and electron probe microanalysis results showed that the film was composed of aluminum nitride, alumina, aluminum, and magnesium. Further, the film showed good adhesion at 0 ks.

Abstract: Reusable spacecraft/supersonic aircraft is research and development towards the realization of a new aerospace transportation system.Because these transport aircraft is to flight at a speed of more than Mach 5,are considering the use of scramjet engine.Because this engine uses air as an oxidant and liquid hydrogen as a fuel,the combustion gas temperature is more than 2500°C.So the combustor is required lightweight material and super-heat-resistant material.In the field of aerospace,SiC-based ceramics that is heat-resistant materials are well known as to maintain the mechanical properties at high temperatures and have a high oxidation resistance.However, this material limit as heat-resistant material is about 1600 °C .Therefore, it can not be used in an environment of scramjet engine combustor.There are the measures by metal structure to be force-cooled by refrigerant fuel,but apply is difficult because the system is complexity and very heavy. In this study use the hafnium-based super heat-resistant ceramics that is having a melting point more than 2000°C. Purpose is to develop a new technique for forming the ceramics mainly composed from Hafnium Carbide (Melting point:3950°C) that is very high melting point and have oxidation resistance by melt impregnation to inside C/C composite.In addition, implement the evaluation of changes in the organization after each process by the cross-sectional observation and strength assessment by three-point bending test.

Abstract: Traditional methods of roughness characterization cannot properly reflect the characteristics of engineering ceramics surface topography. Therefore, the composite characterization using combined fractal method and wavelet method is introduced in this paper. And they are used to describe the global and local characteristics of engineering ceramics ground surface, respectively. Furthermore, a concept called topography damage ratio is proposed to describe characteristic of the deep wave trough. Finally, 3-D measurement is used to verify this method.

Abstract: Rayleigh-Taylor model, an important theory dealing with ferro-hydrodynamic ( FHD ) instability, is utilized to predict the ferro-surface tension in this study. Before hexagonal peaking patterns induced by critical magnetization of ferro-solution, the simplification from proposed theory could be further made under the consideration of normal field imposed, i.e., linear relation of free surface tension proportional to apparent ferro-weight might be successfully predicted. That offers a simple semi-formula easier to study the static ferro-surface tension. To validate above results, a self-designed ring-pull device is set up as auxiliary experimental mechanism. Here relevant test of ferro-sample in various volumetric concentration as well as field intensity will be performed. Consequently, both results accessed from ferro-experiment and theoretic analysis delivers an agreement within the working magnetic intensity 0~40 mT, where a remarkable increase of surface tension coefficient occurs at higher magnetic field for ferro-solution with denser volumetric concentration considered.